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Old 5th December 2008, 03:30 PM   #31
Pano is offline Pano  United States
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Groovy.

I'm Michael, as you know. But most guys on the forums call me "Pano"
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Old 5th December 2008, 04:07 PM   #32
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A friend of mine suggested I do a patent search to see how these commercially available shotgun mics are designed. Makes perfect sense. Now why didn't I think of that? I'll be happy to share my findings.

Thanks to those who let us know who your are. Though this is completely off-topic and should perhaps be addressed to the forum administrators, I guess the more appropriate question would be: "By what name would you like to be addressed on this forum?" When applying for membership, it would be cool to have such a field to fill in. I don't think the "user name" field can address this because I'm not sure they allow duplications, even though many of us have the same birth name. Oh well. Perhaps my user name should be "anal" for I may well be the only person concerned with this.

Scott
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Old 21st December 2008, 04:45 AM   #33
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Hi folks,

In doing a bit of research on the question of shotgun microphone magic, I had been trying to get information on the design and construction of the tv/film "standard", the Sennheiser MKH 416, in an effort to build my own for another purpose. I attempted perusing patents and got way in over my head. However, while visiting other forums, I became intrigued when the Sanken CS-3 kept showing up as a favorable alternative to the Sennheiser MKH 416. The Sanken folks are more forthcoming about their design on various web sites, likely as a marketing tool, so hence I was able to find the following:

http://www.sanken.ch/english/cs-3.htm
http://www.soundmixers.com/index.php...upid=14&pid=51
http://www.trewaudio.com/sankencs3.htm

The Sanken CS-3 utilizes 3 directional condenser capsules spaced just so. The advantages of this type of microphone over those of the "mechanical tube" type, for lack of a better term, are that it cancels better at low frequencies, has less proximity effect, and can be physically shorter. The CS-3 is also lighter, but that may have nothing to do with these electrical vs mechanical approaches. I'm guessing that the MKH 416 is a single capsule "mechanical tube" type?

I may soon begin experimentation with the multiple capsule array in lieu of data on the other type.

Scott Morrison
Van Nuys, CA
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Old 21st December 2008, 10:24 PM   #34
Mark Kravchenko --- www.kravchenko-audio.com
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Default Here are some sources for mic capsules!

Hi Scott

I found some sources for mic capsules that will be of some interest to you if you want to duplicate the Sanken microphone. The ones on page 2194 may bring you a little smile if you recognize them from the drawings that you posted earlier.

http://onlinecatalog.digikey.com/def...PageIndex=2194

Mark
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Old 22nd December 2008, 04:23 PM   #35
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Hi Mark,

Thank you for the resource. However, I think you may have lost me. If you're referring to these Sanken drawings...

http://www.sanken.ch/english/cs-3.htm

...they lack detail and I cannot tell from same if they correspond to a particular Knowles model on that Digikey page. Do you think Sanken is using a particular model of Knowles capsule from that group? Also, there are some other details lacking (probably for good reason) that would prevent a guy like me from producing a CS-3 knockoff.

I've been ordering capsules from Digikey since the late seventies, but always gravitated toward the Panasonic units because they state their frequency response (and I've tested most of them). Knowles and many others do not, so it's pure guess work. (I don't know how on earth they can expect a customer to make a wise decision when such a critical specification as frequency response is missing!) Long ago, I did order one each of the Knowles microphones (not this particular group you just pointed out - too expensive for that) just so I could see if they were usable for my particular application at the time. Well, they sounded horrible. They were all midrange and nothing else, which made sense because they were designed for hearing aids and hence focus on voice frequencies. (They still live in my parts box.)

With this new line of Knowles models that you pointed out, I'd love to know how they sound, but without a published frequency response and each capsule costing upwards of $40, it's an expensive proposition to test even a few. Plus, for the project I'm designing, if I were using as few as 2 shotgun microphones, requiring 6 capsules, it would get very expensive very fast.

Otherwise, I was considering buying some more of my old two-dollar standby's, the Panasonic WM-55A103 (unidirectional) and the Panasonic WM-61A (omnidirectional) (Digikey page 2193) to experiment with this multi-capsule array. They're not the greatest capsules in the world, but they're still pretty good, and the best I could find by cherry-picking Digikey's offerings.

Looking forward to any further insights you may have. Thanks again.

Scott Morrison
Van Nuys, CA
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Old 28th December 2008, 07:01 PM   #36
Mark Kravchenko --- www.kravchenko-audio.com
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Default Stupid is as Stupid Duzz

Hi Scott!

The post I put up about the capsule was a real dumb mistake. Those mics are sub miniatures for hearing aids as you stated. They have a reasponse that is tailored to the gain and losses when place in the ear canal or the ear itself. So pretty much useless.

I am going to be getting home tonight and I will send you the rest of the elektor articles. They are to big to post.

As a group of information they give you what you need to figure out. And most of the circuitry to get it done. There is no reason why you cannot reverse engineer the Sanken mic from the drawings and the specified length. The tube is fairly easy to figure out and the mic capsules that you have on hand are worth a try. The only question that I have is whether or not a directional capsule will work better in this application. My gut tells me that it would but I will read the articles that I post tonight so that I have a bit of a refresher.

Mark

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Old 28th December 2008, 07:31 PM   #37
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Much obliged, Mark, for all the Elector stuff. I've been preoccupied with another project lately so haven't yet been able to experiment with the capsule array for the shotgun microphone but am dying of curiosity and chomping at the bit to get to it. Like you, I suspect that the uni-directional capsules will work best, but you never know.

And for those who give a hoot, I'll post what I learn as I go.

Thanks again,
Scott
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Old 27th November 2011, 06:32 PM   #38
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The theory behind the popular electronics mic is not so different to that of the tubular shotgun mic.
The tube with slots down the side is called an interference tube. Sound waves entering at the end of the tube will travel to the end and all be in phase when they reach the mic capsule therefore will be additive. sound waves entering the tube along the side, i.e. through the slots will enter at different points along the length of the tube and be reflected towards the capsule, sound from different slots will have travelled different distances and will not therefore be in phase at the capsule and will be subtractive to varying degrees.
So to summarise, sound which is subtractive will be at a lower overall level than in phase additive sound, meaning that the higher levels are produced from the front of the tube and those at the sides will be attenuated.

Hope this helps.

Jilly.
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Old 27th November 2011, 08:56 PM   #39
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A similar idea is used in microwave waveguide directional couplers. In fact, I bet the maths isn't that different - circular stuff always seems to end up with Bessel functions.

I wonder if an acoustic version of a Yagi is possible?
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Old 27th November 2011, 09:36 PM   #40
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I think it could be done but would not be s practical, The elements would be enormous, a 1/4 wave element at 1 kHz, 75 Km. Try that on the end of a fishpole.
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